CN109154787B - Carrier for developing electrostatic latent image, developer, image forming apparatus, process cartridge, and image forming method - Google Patents

Abstract

A carrier for developing an electrostatic latent image includes core material particles and a resin layer covering the surfaces of the core material particles. The resin layer includes a resin and at least one kind of fine particles. At least one of the fine particles includes electrically chargeable fine particles. The charged fine particles have a long diameter of 400-900 nm. The charged fine particles have a shape factor SF-1 of 160-250.

Description

Carrier for developing electrostatic latent image, developer, image forming apparatus, process cartridge, and image forming method

Technical Field

The invention relates to a carrier for electrostatic latent image development, a two-component developer, a developer for replenishment, an image forming apparatus, a process cartridge, and an image forming method.

Background

In image formation using an electrophotographic method, an electrostatic latent image is formed on an electrostatic latent image carrier made of a photosensitive material, a toner image is formed by supplying charged toner to the electrostatic latent image, and then the resultant toner image is transferred to a recording medium and fixed to form an output image. In recent years, technologies (technical apparatuses, technologies) using an electrophotographic method, such as copiers and printers, are rapidly advancing from technologies using a monochrome (black and white) electrophotographic method to technologies using a full-color electrophotographic method, and the market for technologies using a full-color electrophotographic method is expanding.

Generally, in full-color image formation, three color toners (color toners) of yellow, magenta, and cyan, or black and four color toners of yellow, magenta, and cyan are stacked to reproduce all colors. Therefore, in order to obtain a clear (sharp) full-color image excellent in color reproducibility, it is necessary to smooth the surface of the fixed toner image to reduce light scattering. For these reasons, the gloss of images obtained by means of conventional full-color copiers and the like is usually moderately high (i.e., 10% to 50%).

Conventionally, as a method of fixing a dry-toner image on a recording medium, a contact-heating fixing method in which a roller or belt having a smooth surface is brought into pressure contact with toner while heating the roller or belt is often used. The method has the advantages that: it exhibits high heat efficiency, realizes high-speed fixing, and enables a colored toner image to have glossiness and transparency. On the other hand, this method inconveniently causes a so-called offset phenomenon in which a part of the toner image adheres to the surface of the fixing roller and is then transferred onto another image, because the surface of the heated fixing member is brought into contact with the melted toner under pressure and then they are separated from each other.

In order to prevent such a shift phenomenon, the following method has been implemented: the surface layer of the fixing roller is formed by using a material excellent in releasability, such as silicone rubber or fluororesin, and further a toner adhesion preventing oil (such as silicone oil) is applied to the surface layer of the fixing roller. Although this method is extremely effective in preventing toner offset, it requires an additional provision of a device for replenishing the oil, resulting in an increase in size of the fixing device.

As a result, in monochrome image formation, a system in which the following toner is used to omit an oil-less system in which oil is applied to a fixing roller, or a system in which the toner is used to make the amount of application of oil very small is increasingly used: the toner has high viscoelasticity when melted and contains a release agent in order to avoid internal cracking of the melted toner.

Meanwhile, also in full-color image formation, in order to miniaturize the fixing device and simplify the structure, an oil-less system tends to be used, and also in monochrome image formation. However, in full-color image formation, there are needs as follows: the surface of the fixed toner image is smoothed, and thus the viscoelasticity of the toner in a molten state is reduced. Therefore, full-color image formation can more easily cause the shift phenomenon than monochrome image formation (which produces less glossiness), and full-color image formation becomes more difficult to use the oil-less system. When a toner containing a release agent is used, the adhesive strength of the toner increases, so that the transferability of the toner to a recording medium deteriorates. Further, the use of a toner containing a release agent disadvantageously causes filming of the toner, resulting in deterioration of chargeability and then durability.

Meanwhile, as a carrier designed to satisfy, for example, the following object, a carrier whose surface is coated with a resin layer containing carbon black is known: preventing filming of the toner, forming a uniform surface, preventing surface oxidation and deterioration of moisture sensitivity, extending the life of the developer, preventing adhesion on the photoreceptor surface, protecting the photoreceptor from scratches and abrasion (scraping), controlling charge polarity, and regulating charge amount. Such a support can form a good image at the beginning. However, the image quality deteriorates due to abrasion of the resin layer as the number of copies increases. In addition, color contamination occurs due to abrasion of the resin layer or separation of carbon black from the resin layer. As an alternative material to carbon black, titanium oxide, zinc oxide, and the like are generally known. However, these materials do not provide a sufficient effect of lowering the volume resistivity. In addition, the image may be disturbed by a resistance change caused by exposure of the core material due to stress separation of fine particles included in the resin layer. To cope with this, PTL 1 discloses a technique of: the separation is reduced by dispersing conductive fine particles having a large shape factor SF-1 treated with an ionic liquid in a resin layer to increase an adhesion area between the resin and the conductive fine particles.

In the field of production printing in which the market has increased in recent years, higher image quality than ever is required. It is technically extremely difficult for a machine to individually cope with density fluctuation (fluctuation) and density unevenness of an image on one sheet and density fluctuation between images when tens of thousands of sheets are printed. For this reason, it is necessary to control the charged amount of the toner at a more constant level than before. However, the conventional carriers described above cannot satisfy the required properties. In recent years, the toner tends to be fixed at a low temperature to reduce power consumption. In order to fix the toner at a low temperature, the amount of the fine particles needs to be reduced. As a result, the toner is disadvantageously scattered due to: insufficient charging of the toner due to insufficient mixing of the toner and the developer at the time of replenishment. In a system in which the chargeability of a carrier mainly determines the chargeability of toner, it is necessary to maintain the charge imparting ability of the carrier in a stable state from the start of printing until after tens of thousands of sheets are printed.

Disclosure of Invention

Technical problem

The present disclosure has an object to provide a carrier for electrostatic latent image development: which has sufficient charging ability, is capable of supplying a stable amount of developer to a developing zone, and is capable of providing image quality required in the field of production printing even in a high-speed machine using a toner fixed at a low temperature.

Solution to the problem

According to one aspect of the present invention, a carrier for developing an electrostatic latent image includes core material particles and a resin layer covering surfaces of the core material particles. The resin layer contains a resin and at least one kind of fine particles. At least one of the fine particles includes electrically chargeable fine particles. The charged fine particles have a long diameter of 400-900 nm. The charged fine particles have a shape factor SF-1 of 160-250.

Advantageous effects of the invention

According to the present invention, there can be provided a carrier for electrostatic latent image development: which has sufficient chargeability, is capable of supplying a stable amount of developer to a developing zone, and is capable of providing image quality required in the field of production printing even in a high-speed machine using a toner fixed at a low temperature.

Drawings

Fig. 1 is a view illustrating a unit for measuring a volume resistivity of a carrier for electrostatic latent image development according to the present invention.

Fig. 2 is a view illustrating one example of the process cartridge according to the present invention.

Detailed Description

The carrier for electrostatic latent image development according to the present invention (hereinafter may be simply referred to as carrier) will be described in detail.

The carrier for developing an electrostatic latent image according to the present invention includes a core material particle and a resin layer covering the surface of the particle. The resin layer contains a resin and at least one kind of fine particles. At least one of the particles is a charged fine particle. The charged fine particles have a long diameter of 400-900 nm. The charged fine particles have a shape factor SF-1 of 160-250.

The chargeable fine particles according to the present invention refer to fine particles that exhibit opposite chargeability to toner and impart, for example, negative chargeability to toner by friction with toner. The charging is imparted by frictional contact with the toner and thus a part of the chargeable fine particles is preferably exposed on the surface of the resin layer. According to this form, not only the charging property is improved, but also the charging property can be maintained even after an image having a high image area is output for a long period of time. Examples of the chargeable fine particles in the case of imparting, for example, negative chargeability to the toner include barium sulfate, magnesium hydroxide, magnesium oxide, hydrotalcite, and zinc oxide. Among them, barium sulfate is preferable.

It is desirable that the long diameter of the chargeable fine particles is 400nm or more and 900nm or less. The long diameter is less than 400nm, and the chargeability of the carrier may be unstable. The reason for this includes that the chargeable fine particles are difficult to be exposed on the resin layer. The long diameter of the chargeable fine particles is preferably 600nm or more from the viewpoint of improving chargeability and developability. In contrast, the chargeable fine particles having a long diameter of more than 900nm are not preferable because the chargeable fine particles may be separated from the resin layer.

The long diameter of the chargeable fine particles according to the present invention is measured by the following method.

The carrier was mixed in embedding (embed) resin (two-part mixing type epoxy resin manufactured by Devcon, inc. cured for 30 minutes) and allowed to cure overnight. A thick section sample was prepared from the cured sample by mechanical grinding (polish). The cross section of the crude sample was subjected to finish machining under conditions of 5.0kV acceleration voltage and 120 μ a beam current by using a cross-section grinder (polisher, SM-09010, manufactured by JEOL ltd.). The cross section of the finished sample was photographed under a condition of 0.8kV acceleration voltage and 30,000 times magnification using a scanning electron microscope (Merlin, manufactured by Carl Zeiss AG). The photographed image is converted into a TIFF image. The long diameters of the chargeable fine particles of 100 particles were measured using Image-Pro Plus manufactured by Media Cybernetics inc and the average value of the long diameters was determined as the long diameters of the chargeable fine particles according to the present invention.

According to the present invention, it is required that the shape factor SF-1 of the chargeable fine particles is 160 or more and 250 or less.

The shape factor SF-1 represents sphericity (sphericity). As the shape factor SF-1 increases from 140, the shape of the chargeable fine particles gradually changes from a spherical shape to a flat shape (flat shape), an irregular shape. The chargeable fine particles having a shape factor SF-1 of 160 or more may be exposed on the surface of the resin layer and thus may impart sufficient chargeability to the support. For example, when the resin layer is provided by spraying, particularly by coating using a two-fluid nozzle, the electrically chargeable fine particles having a shape factor SF-1 of 160 or more may be parallel to the core material particles. The following is conceivable: this phenomenon occurs because the chargeable fine particles follow the flow of the resin when the spray droplets fall on the surface of the core material particles and are leveled. As a result, when the chargeable fine particles having the shape factor SF-1 of less than 160 are used, satisfactory chargeable fine particles cannot be exhibited unless the chargeable fine particles are exposed due to abrasion of the resin by printing stress. In contrast, when the chargeable fine particles having the shape factor SF-1 of 160 or more are used, many chargeable fine particles are exposed on the surface of the support from the start of printing and thus sufficient chargeability can be provided. If it is desired to increase the exposed surface of the fine particles from the start of printing in the case of using chargeable fine particles having a shape factor SF-1 of less than 160, the following is conceivable as a possible solution: the ratio of the particle size of the chargeable fine particles to the thickness of the resin layer was changed. However, in this case, the fine particles may be separated due to a decrease in the adhesion area between the resin and the chargeable fine particles. Another option is to add charge control agents. By adding the charging control agent, initial charging properties can be ensured by the charging control agent and a part of the exposed surface of the chargeable fine particles. However, when the resin layer is abraded by printing stress, the exposure amount of the chargeable fine particles is significantly changed, so that the charge amount distribution of the toner also fluctuates. As a result, the charge amount of the toner rapidly increases with the increase in the print amount and the color tone of the printed image becomes uneven, resulting in a deterioration in print quality. According to the present invention, chargeable fine particles having a shape factor SF-1 of 160 or more are used. As a result, fluctuation of the exposed area when the resin covering the charged fine particles is abraded becomes small and as a result, stable charging property can be exhibited.

Further, it is desirable that the shape factor SF-1 of the chargeable fine particles be 250 or less. When the chargeable fine particles having a shape factor SF-1 of more than 250 are used, that is, when the chargeable fine particles having a very high flatness are used, the sphericity remarkably disappears and the irregularities of the support surface become minute. The toner resin, wax, additive, and the like are selectively consumed (consumed) into the recessed portions (recesses) formed due to the presence of fine particles in the resin layer. However, when the irregularity is minute, the consumption amount in the recess increases and the function of the recess is impaired. The charging decreases when the charge control agent is located in the recess, and the resistance increases when the resistance control agent is located in the recess.

According to the present invention, the shape factor SF-1 of the chargeable fine particles is more preferably 190-210.

The shape factor SF-1 according to the present invention is measured by the following method. By using a scanning electron microscope (S-800, manufactured by Hitachi, ltd.), charged fine particle images were sampled randomly and image information thereof was led to and analyzed by an image analyzer (Luzex3) manufactured by Nicolet co, ltd. via an interface, followed by calculating the shape factor SF-1 using the following formula.

SF-1＝((MXLNG)2/AREA))(100π/4)

Here, MXLNG denotes the absolute maximum length of the electrically charged fine particles and AREA denotes the projected AREA of the electrically charged fine particles.

According to the invention, 100 charged fine particles are sampled randomly and the average of the measured values is determined as SF-1 according to the invention.

It is important that the chargeable fine particles are contained in the resin layer. As described above, the charging property of the carrier is sufficiently improved by exposing the charging fine particles on the surface layer of the carrier. However, if the surface of the chargeable fine particles is covered with a substance such as tin, the chargeable property is not sufficiently ensured because the charged portions of the chargeable fine particles are not exposed on the surface layer. For this reason, it is difficult to exhibit stable chargeability. Further, the exposure of the chargeable fine particles on the surface layer of the carrier provides an effect of easily capturing the replenished toner. The following is conceivable: this phenomenon is caused by easily charging the chargeable fine particles and the toner by friction. As a result, this phenomenon is extremely effective for toners in which charged particles are reduced for fixing at low temperatures. The charged fine particles may be partially covered with a substance such as tin. However, in this case, the coverage of the chargeable fine particles with respect to the surface is preferably less than 10%.

The shape of the electrically charged fine particles can be adjusted by appropriately adjusting the reaction conditions such as the reaction rate and the stirring speed at the time of producing the electrically charged fine particles.

According to the present invention, the thickness of the resin layer is preferably 0.2 μm or more and 2.0 μm or less, and thus the advantageous effects of the present invention can be further improved. The chargeable fine particles having a resin layer thickness of 0.2 μm or more do not cause excessive exposure of the chargeable fine particles and do not provide excessively high chargeability of the support. Therefore, the charging adjustment can be appropriately performed from the start of printing. In addition, the chargeable fine particles are difficult to separate because a sufficient contact surface area between the chargeable fine particles and the resin can be obtained. Further, the chargeable fine particles having a resin layer thickness of 2.0 μm or more allow the toner to be sufficiently charged even when the film abrasion does not proceed, because the charged fine particles are appropriately exposed from the start of printing.

According to the present invention, the thickness of the resin layer is more preferably 0.4 μm or more and 1.5 μm or less.

The thickness of the resin layer according to the present invention is measured by the following method. The carrier was mixed in embedding resin (a two-part hybrid epoxy resin manufactured by Devcon, inc., cured for 30 minutes) and allowed to cure overnight. A thick section sample was prepared from the cured product by mechanical milling. The cross section of the crude sample was subjected to finish machining under conditions of 5.0kV acceleration voltage and 120 μ a beam current by using a cross-section grinder (SM-09010, manufactured by JEOL ltd.). The cross section of the finished sample was photographed under a condition of 0.8kV acceleration voltage and 30,000 times magnification using a scanning electron microscope (Merlin, manufactured by Carl Zeiss AG). The photographed image is converted into a TIFF image. The thickness of the resin layer in the field of view was measured using Image-Pro Plus manufactured by Media Cybernetics inc and the average value of the thickness was determined. Similarly, the thickness of the resin layer of 100 particles of the carrier particles was measured and the average value thereof was determined as the thickness of the resin layer according to the present invention.

The resin layer of the support according to the invention is preferably obtained by: the following copolymers obtained by radical copolymerization of the following a and B components are hydrolyzed to form silanol groups, crosslinked by condensation using a catalyst, the surface of the core material particles is coated, and thereafter the particles are subjected to a heat treatment:

in the chemical formula, R¹、m、R²、R³X and y are shown below.

R¹: hydrogen atom or methyl group

m: an integer of 1 to 8

R²: hydrocarbon groups having 1 to 4 carbon atoms, e.g. alkyl groups such as methyl, ethyl, propyl, isopropyl and butyl

R³: alkyl groups having 1 to 8 carbon atoms such as methyl, ethyl, propyl, isopropyl and butyl, or alkoxy groups having 1 to 4 carbon atoms such as methoxy, ethoxy, propoxy and butoxy.

The component A comprises:

in the chemical formula, R¹M and R²As described above.

For the a component, X is 10 mole% to 90 mole% and more preferably 30 mole% to 70 mole%.

For example, the a component has tris (trimethylsiloxy) silane, which is an atomic group in which a large number of methyl groups are present in the side chain. As the ratio of the a component to the entire resin increases, the surface energy decreases and thus the adhesion of the resin component and the wax component in the toner decreases. If the ratio of the A component is less than 10 mol%, a sufficient effect is not obtained and thus the adhesive force of the toner component is significantly increased. On the other hand, if the ratio of the A component is higher than 90 mol%, the B component B and the C component described below are reduced. As a result, the crosslinking cannot proceed and toughness becomes insufficient and adhesiveness between the core material particles and the resin layer is lowered and durability of the carrier coating film becomes poor.

R²Is an alkyl group having 1 to 4 carbon atomsAnd examples of such monomer components include tris (trialkylsiloxy) silane compounds represented by the following formula.

In the formula, Me, Et and Pr denote methyl, ethyl and propyl, respectively.

CH₂＝CMe-COO-C₃H6-Si(OSiMe₃)₃

CH₂＝CH-COO-C₃H₆-Si(OSiMe₃)₃

CH₂＝CMe-COO-C₄H₈-Si(OSiMe₃)₃

CH₂＝CMe-COO-C₃H₆-Si(OSiEt₃)₃

CH₂＝CH-COO-C₃H₆-Si(OSiEt₃)₃

CH₂＝CMe-COO-C₄H₈-Si(OSiEt₃)₃

CH₂＝CMe-COO-C₃H₆-Si(OSiPr₃)₃

CH₂＝CH-COO-C₃H₆-Si(OSiPr₃)₃

CH₂＝CMe-COO-C₄H₈-Si(OSiPr₃)₃

The method for producing the a component is not particularly limited. The A component is obtained by a method of reacting tris (trialkylsiloxy) silane and allyl acrylate or allyl methacrylate in the presence of a platinum catalyst, or a method of reacting methacryloxyalkyltrialkoxysilane and hexaalkyldisiloxane in the presence of a carboxylic acid and an acid catalyst as described in Japanese unexamined patent application publication No. H11-217389.

And B component: (crosslinking component)

In the chemical formula, R¹、m、R²And R³As described above.

That is, the B component is a radically polymerizable bifunctional or trifunctional silane compound and Y is 10 mol% to 90 mol% and more preferably 30 mol% to 70 mol%. If the ratio of the B component is less than 10 mol%, toughness cannot be sufficiently obtained. On the other hand, if the ratio of the B component is higher than 90 mol%, a hard and brittle coating film is generated and thus the coating film may be abraded. In addition, environmental properties of the coating film deteriorate. The following is conceivable: many hydrolyzed crosslinking components remain as silanol groups to deteriorate environmental properties (humidity dependence).

Examples of such monomer components include

3-methacryloxypropyltrimethoxysilane,

3-acryloxypropyltrimethoxysilane,

3-methacryloxypropyltriethoxysilane,

3-acryloxypropyltriethoxysilane,

3-methacryloxypropylmethyldimethoxysilane,

3-methacryloxypropylmethyldiethoxysilane,

3-methacryloxypropyltri (isopropoxy) silane, and

3-acryloxypropyltri (isopropoxy) silane.

According to the present invention, an acrylic compound (monomer) may be added as the C component in addition to the a component and the B component.

And C, component C:

examples of the copolymer to which such a C component is added include the following copolymers.

In the formula, R¹、m、R²And R³As described above. X is 10 to 40 mol%, Y is 10 to 40 mol%, Z is 30 to 80 mol%, and 60 mol%<Y+Z<90 mol%.

The C component imparts flexibility to the resin layer and improves adhesion between the core material particles and the resin layer. However, if the ratio of the C component is less than 30 mol%, sufficient adhesion is not obtained. If the ratio of the C component is higher than 80 mol%, the ratio of the a component or the ratio of the B component becomes 10 mol% or less, and therefore the water repellency, hardness, and flexibility (film abrasion) of the resin layer are difficult to all satisfy at the same time.

Preferable examples of the acrylic compound (monomer) of the C component include acrylic acid esters and methacrylic acid esters, and specific examples thereof include methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate, butyl acrylate, 2- (dimethylamino) ethyl methacrylate, 2- (dimethylamino) ethyl acrylate, 3- (dimethylamino) propyl methacrylate and 3- (dimethylamino) propyl acrylate. Among them, alkyl methacrylate is preferable, and methyl methacrylate is particularly preferable. These compounds may be used alone or in combination of two or more of them.

A technique of improving durability by crosslinking a resin layer is described in japanese patent No. 3691115. Japanese patent No.3691115 has disclosed a technique of a carrier for electrostatic image development in which the surface of magnetic particles is covered with a thermosetting resin obtained by: crosslinking a copolymer of an organopolysiloxane having a vinyl group at least at a terminal thereof and a radically copolymerizable monomer having at least one functional group selected from the group consisting of a hydroxyl group, an amino group, an amide group, and an imide group with an isocyanate compound. However, at present, the durability of the resin layer in terms of peeling/abrasion is not sufficiently obtained.

Although the reason for this is not sufficiently clear, in the case of a thermosetting resin obtained by crosslinking the copolymer and the isocyanate compound, as can be seen from the structural formula, the amount of functional groups that react with (crosslink) the isocyanate compound per unit weight in the copolymer resin is small and therefore, a two-dimensional or three-dimensional dense crosslinked structure is not formed at the crosslinking point. For this reason, it is presumed that the long-term use of the carrier for electrostatic image development may cause peeling/abrasion of the resin layer (the abrasion resistance of the coating film is low) and thus sufficient durability is not obtained.

The occurrence of peeling/abrasion of the resin layer leads to a change in image quality and carrier adhesion due to a decrease in the carrier resistance. The peeling/abrasion of the resin layer lowers the fluidity of the developer and results in a reduction in the amount of the developer scooped up. As a result, peeling/abrasion of the resin layer leads to a decrease in image density, staining (scumming) due to an increase in TC, and toner scattering.

The resin used in the present invention is a copolymer having a large amount of bifunctional or trifunctional crosslinkable functional groups (dots) per unit weight of the resin (as much as two to three times as much per unit weight), and is obtained by further crosslinking the copolymer via polycondensation. Thus, the following is conceivable: the coating film is extremely tough and hardly abraded, and as a result, high durability is achieved.

The crosslinking by siloxane bonds according to the invention is greater in bond energy and more stable to thermal stress than the crosslinking by isocyanate compounds. Therefore, it is presumed that the stability of the resin layer with time is maintained.

As the resin used in the resin layer according to the present invention, a silicone resin, an acrylic resin, or a combination thereof may be used in addition to the above-described resins. Acrylic resins have strong adhesion and low brittleness and thus have very excellent wear resistance. On the other hand, however, the acrylic resin may cause troubles due to the high surface energy of the acrylic resin, such as a decrease in charge amount due to accumulation of consumed toner components in the case of combination with a toner that may be consumed. In this case, the problem can be solved by using a silicone resin that is less likely to consume toner components due to low surface energy, and an effect of reducing the accumulation of consumed components due to film abrasion can be provided by the acrylic resin. However, silicone resins have low adhesion and high brittleness, and therefore also have the weakness of poor abrasion resistance and therefore, it is important to obtain a good balance of the properties of the two resins. As a result, these balanced properties allow obtaining a coating film having difficulty in accumulation of consumables and having wear resistance.

The silicone resin described in the present specification refers to all publicly known silicone resins and examples of the silicone resin include linear silicone resins composed solely of organosiloxane bonds and silicone resins modified with alkyd, polyester, epoxy, acrylic, urethane, or the like. However, the silicone resin is not limited to these examples. Examples of commercially available products of the linear Silicone resin include KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical co., ltd., and SR2400, SR2406, and SR2410 manufactured by Dow Corning Toray Silicone co., ltd. In these cases, although a separate silicone resin may be used, the silicone resin may also be used simultaneously with other components that may cause a crosslinking reaction, a charge amount adjusting component, and the like. Examples of modified Silicone resins include KR206 (alkyd-modified), KR5208 (acrylic-modified), ES1001N (epoxy-modified) and KR305 (urethane-modified) manufactured by Shin-Etsu Chemical co.

In order to adjust the volume resistivity of the carrier, the resin layer according to the present invention preferably includes conductive fine particles. The conductive fine particles are not particularly limited. Examples of the conductive fine particles include carbon black and fine particles of ITO, PTO, WTO, tin oxide, zinc oxide, and conductive polymers such as polyaniline. These conductive fine particles may be used in combination of two or more of them.

The support according to the invention preferably has a volume-average particle size of 28 to 40 μm. Carrier particles having a volume-average particle size of less than 28 μm may cause carrier adhesion, while carrier particles having a volume-average particle size of more than 40 μm cause a decrease in reproducibility of image details and may fail to form a fine image.

The volume average particle size can be measured using, for example, a Microtrac particle size distribution meter of the type HRA 9320-X100 (manufactured by NIKKISO co., ltd.).

The carrier according to the present invention preferably has a volume resistivity of 8 to 16(Log Ω · cm). A carrier with a volume resistivity below 8(Log Ω · cm) may result in carrier adhesion in the non-image areas, while a carrier with a volume resistivity above 16(Log Ω · cm) may cause unacceptable levels of edge effects.

The volume resistivity can be measured by using the cell shown in fig. 1. Specifically, the support 3 was first filled in a unit made of a fluororesin container 2 accommodating an electrode 1a and an electrode 1b having a surface area of 2.5cm × 4cm at a distance of 0.2cm, and then tapped ten times at a tapping speed of 30 times/minute from a falling height of 1 cm. Subsequently, a direct current voltage of 1,000V was applied between the electrodes 1a and 1b, and the resistance r [ Ω ] after 30 seconds of application was measured by using a high-resistance meter 4329A (manufactured by Yokogawa Hewlett Packard, co., ltd.). The volume resistivity [ Ω · cm ] can be calculated by the following formula:

r·(2.5·4)/0.2。

examples of the polycondensation catalyst include titanium-based catalysts, tin-based catalysts, zirconium-based catalysts, and aluminum-based catalysts. Among these catalysts, diisopropoxybis (titanium ethylacetoacetate) is the most preferred catalyst among the titanium based catalysts that provide excellent results according to the present invention. The following is conceivable: this is because the catalyst is highly effective for promoting the condensation reaction of the silanol groups and is difficult to deactivate.

According to the present invention, when a silicone resin is used for the resin layer, a silane coupling agent is preferably used in combination with the silicone resin. This combination allows the fine particles to be stably dispersed.

The silane coupling agent is not particularly limited. Examples of the silane coupling agent include gamma- (2-aminoethyl) aminopropyltrimethoxysilane, gamma- (2-aminoethyl) aminopropylmethyldimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, N-beta- (N-vinylbenzylaminoethyl) -gamma-aminopropyltrimethoxysilane hydrochloride, gamma-glycidoxypropyltrimethoxysilane, gamma-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, gamma-chloropropyltrimethoxysilane, hexamethyldisilazane, gamma-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl ] ammonium chloride, gamma-glycidyloxypropyltrimethoxysilane, gamma-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, gamma-chloropropyltrimethoxysilane, hexamethyldisilazane, gamma-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl ] ammonium chloride, and the like, Gamma-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1, 3-divinyltetramethyldisilazane, and methacryloyloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride. These silanes may be used in combination of two or more of them.

Examples of commercially available products of silane coupling agents include AY43-059, SR6020, SZ6023, SH6026, SZ6032, SZ6050, AY43-310M, SZ6030, SH6040, AY43-026, AY43-031, SH6062, Z-6911, SZ6300, SZ6075, SZ6079, SZ6083, SZ6070, SZ6072, Z-6721, AY43-004, Z-6187, AY43-021, AY43-043, AY43-040, AY43-047, Z-6265, AY43-204M, AY43-048, Z-6403, AY 43-206-E, Z-6341, AY 43-MC 210, AY43-083 101, AY-4684-4642, AY-699, AY 43-460, and AY 3946 (manufactured by Llicy).

The amount of the silane coupling agent added is preferably 0.1 to 10 mass% with respect to the silicone resin. When the added amount of the silane coupling agent is less than 0.1% by mass, the adhesiveness between the core material particles and fine particles and the silicone resin is lowered, and thus the resin layer is sometimes exfoliated during long-term use, whereas when the added amount of the silane coupling agent is more than 10% by mass, filming of the toner is sometimes occurred during long-term use.

According to the present invention, the core material particles are not particularly limited as long as the particles are a magnetic material. Examples of the magnetic substance include ferromagnetic metals such as iron and cobalt; iron oxides such as magnetite, hematite, and ferrite; various alloys and compounds; and resin particles in which the magnetic substance is dispersed in a resin. Among them, from the viewpoint of environmental protection, Mn-based ferrites, Mn-Mg-Sr-based ferrites, and the like are preferable.

According to the present invention, the chargeable fine particles are preferably used in an amount of 40 to 220 mass%, and more preferably 80 to 140 mass% with respect to the resin.

The two-component developer according to the present invention (which may be hereinafter referred to as a developer) has a carrier according to the present invention and a toner.

The toner includes a binder resin and a colorant and may be a monochromatic toner or a chromatic toner. For application to an oil-less system in which oil for preventing toner adhesion is not applied to the fixing roller, the toner particles may include a release agent. Generally, such toners may cause filming. However, the carrier according to the present invention can reduce filming and therefore the developer according to the present invention can maintain good quality for a long period of time. Color toners, in particular, rehmannia color toners, generally have the problem of generating color contamination due to abrasion of the coating layer of the support. However, the developer according to the present invention can reduce the generation of color contamination.

The toner can be manufactured using a known method such as a pulverization method or a polymerization method. For example, when the toner is manufactured using a pulverization method, first, a melt-kneaded material obtained by kneading toner raw materials is cooled, and then pulverized and classified to prepare mother particles (base particles). Subsequently, in order to further improve transferability and durability, an external additive is added to the mother particle to prepare a toner.

Examples of the apparatus for kneading the toner material at this time include, but are not limited to, a batch type twin-roll machine; an internal mixer; continuous twin-screw extruders such as KTK type twin-screw extruder (manufactured by Kobe Steel Ltd.), TEM type twin-screw extruder (manufactured by Toshiba Machine co., Ltd.), twin-screw extruder (manufactured by ASADA IRON WORKS co., Ltd.), PCM type twin-screw extruder (manufactured by egikai IRON WORKS co., Ltd.), and KEX type twin-screw extruder (manufactured by kuroto, Ltd.); and a continuous type single screw kneader such as a co-kneader (which is manufactured by BUSS AG).

In pulverizing the cooled melt-kneaded material, the cooled melt-kneaded material may be coarsely pulverized using a hammer mill, Rotoplex, or the like, and then may be finely pulverized using a fine pulverizer using a jet stream, a mechanical type pulverizer, or the like. The cooled melt-kneaded material is preferably pulverized so that the pulverized melt-kneaded material has an average particle size of 3 μm to 15 μm.

The pulverized melt-kneaded material may be classified using a pneumatic separator or the like. The pulverized melt-kneaded material is preferably classified so that the average particle size of the mother particles is 5 μm to 20 μm.

In adding the external additive to the mother particle, the external additive is attached to the surface of the mother particle while the external additive is disintegrated (disintegrated) by mixing and stirring using a mixer.

The binder resin is not particularly limited. Examples of the binder resin include: homopolymers of styrene and its substituted products, such as polystyrene, poly-p-styrene and polyvinyltoluene; styrene-based copolymers such as styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene- α -chloromethyl methyl acrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, and aromatic petroleum resin. These binder resins may be used in combination of two or more of them.

The binder resin for pressure fixing is not particularly limited. Examples of the binder resin for pressure fixation include polyolefins such as low-molecular-weight polyethylene or low-molecular-weight polypropylene; olefin copolymers such as ethylene-acrylic acid copolymers, ethylene-acrylic ester copolymers, styrene-methacrylic acid copolymers, ethylene-methacrylic ester copolymers, ethylene-vinyl chloride copolymers, ethylene-vinyl acetate copolymers, and ionomer resins; epoxy resins, polyesters, styrene-butadiene copolymers, polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride copolymers, maleic acid-modified phenolic resins, and phenol-modified terpene resins. These binder resins for pressure fixing may be used in combination of two or more of them.

The colorant (pigment or dye) is not particularly limited. Examples of the colorant include: yellow pigments such as cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow (novel yellow), naphthol yellow S, hansa yellow G, hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG and tartrazine lake; orange pigments such as molybdate orange, permanent orange GTR, pyrazolone orange, Barlerdry orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK; red pigments such as iron oxide red, cadmium red, permanent red 4R, lithol red, pyrazolone red, warm red calcium salt (pigment), lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, and brilliant carmine 3B; violet pigments such as fast violet B and methyl violet lake; blue pigments such as cobalt blue, alkali blue, victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue, and indanthrene blue BC; green pigments such as chromium green, chromium oxide, pigment green B, and malachite green lake; and black pigments such as carbon black, oil furnace black, flue black, lamp black, acetylene black, azine-based pigments such as aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. These colorants may be used in combination of two or more.

The release agent is not particularly limited. Examples of the release agent include polyolefins such as polyethylene and polypropylene, metal salts of fatty acids, fatty acid esters, paraffin waxes, amide waxes, polyhydric alcohol waxes, silicone varnishes, carnauba waxes, and ester waxes. These release agents may be used in combination of two or more of them.

The toner may further include a charge controlling agent. The charge control agent is not particularly limited. Examples of the charging control agent include nigrosine; azine-based dyes having an alkyl group having 2 to 16 carbon atoms (see japanese examined patent application publication No. s 42-1627); basic dyes, such as c.i. basic yellow 2 (c.i.41000), c.i. basic yellow 3, c.i. basic red 1(c.i.45160), c.i. basic red 9(c.i.42500), c.i. basic violet 1(c.i.42535), c.i. basic violet 3(c.i.42555), c.i. basic violet 10(c.i.45170), c.i. basic violet 14(c.i.42510), c.i. basic blue 1(c.i.42025), c.i. basic blue 3(c.i.51005), c.i. basic blue 5(c.i.42140), c.i. basic blue 7(c.i.42595), c.i. basic blue 9 (c.i.i.15), c.i. basic blue 24(c.i.52030), c.i. basic blue 25 (c.i.i. basic blue 42025), c.i. basic blue (c.i.i.i.i. basic blue 42025), c.i. basic blue 45 (c.i.i.52026), and c.i. basic blue 52040; lake pigments of these basic dyes; quaternary ammonium salts such as c.i. solvent black 8(c.i.26150), phenacylcetylammonium chloride and decyltrimethylchloride; dialkyltin compounds such as dibutyltin and dioctyltin; a dialkyltin borate compound; a guanidine derivative; polyamine resins such as vinyl polymers having amino groups and condensation polymers having amino groups; metal complex salts of monoazo dyes described in japanese examined patent application publication No, S41-20153, japanese examined patent application publication No. S43-27596, japanese examined patent publication No. S44-6397 and japanese examined patent publication No. S45-26478; salicylic acid described in Japanese examined patent publication No. S55-42752 and Japanese examined patent publication No. S59-7385; metal complexes of Zn, Al, Co, Cr, Fe, etc., of dialkylsalicylic acid, naphthoic acid and dicarboxylic acid; sulfonated copper phthalocyanine pigments; an organic boron salt; a fluorine-containing quaternary ammonium salt; and, a calixarene compound. These charge control agents may be used in combination of two or more of them. For the color toners other than black, white metal salts of salicylic acid derivatives and the like are preferable.

The external additive is not particularly limited. Examples of the external additive include inorganic particles such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, and boron nitride; and resin particles having an average particle size of 0.05 μm to 1 μm obtained by a soap-free emulsion polymerization method, such as polymethyl methacrylate particles and polystyrene particles. These external additives may be used in combination of two or more of them. Among them, metal oxide particles having a hydrophobized surface such as silica and titania are preferable. The toner having excellent charging stability can be obtained by using both the silica subjected to the hydrophobizing treatment and the titanium oxide subjected to the hydrophobizing treatment and adding an amount of the titanium oxide subjected to the hydrophobizing treatment that is higher than the amount of the silica subjected to the hydrophobizing treatment.

The carrier according to the present invention is used as a developer for replenishment made of the carrier and toner, and the developer for replenishment is applied to an image forming apparatus which forms an image while discharging an excess developer in the developing apparatus, and thus stable image quality can be obtained for an extremely long period of time. That is, the deteriorated carrier in the developing device is replaced with the carrier that is not deteriorated in the replenishment developer, and thus the charge amount is stably maintained for a long period of time and a stable image can be obtained. This method is particularly effective in printing of high image areas. In printing an image having a high image area, carrier charging deterioration due to toner consumption on the carrier is a major carrier deterioration. However, by using this method, the amount of the replenished carrier also increases when printing an image having a high image area and thus the exchange frequency of the deteriorated carrier increases. This allows a stable image to be obtained for an extremely long period of time.

The mixing ratio of the developer for replenishment is preferably a ratio of 2 parts by mass to 50 parts by mass of the toner to be added to 1 part by mass of the carrier. When the toner is less than 2 parts by mass, the amount of the supply carrier is excessive, resulting in an excessive supply of the carrier. This results in an excessively high carrier concentration in the developing device and thus the charge amount of the developer may increase. In addition, as the charge amount of the developer increases, the developing ability (ability) decreases and the image density decreases. When the toner is more than 50 parts by mass, the ratio of the carrier in the developer for replenishment becomes small, and therefore the exchange of the carrier in the image forming apparatus decreases. As a result, the effect of resisting deterioration of the carrier cannot be expected.

(image Forming method)

An image forming method according to the present invention includes: forming an electrostatic latent image on an electrostatic latent image carrier, developing the electrostatic latent image formed on the electrostatic latent image carrier with a developer according to the present invention to form a toner image, transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and fixing the toner image transferred to the recording medium.

(image Forming apparatus)

An image forming apparatus according to the present invention includes an electrostatic latent image carrier, a charging unit that charges the latent image carrier, an exposure unit that forms an electrostatic latent image on the latent image carrier, a developing unit that develops the electrostatic latent image formed on the electrostatic latent image carrier with a developer to form a toner image, a transfer unit that transfers the toner image formed on the electrostatic latent image carrier to a recording medium, and a fixing unit that fixes the toner image transferred to the recording medium. The image forming apparatus further includes other units such as a static electricity eliminating unit, a cleaning unit, a recovery unit, and a control unit, if necessary. The image forming apparatus uses the developer according to the present invention as the developer.

In fig. 2, an example of a process cartridge according to the invention is shown. The process cartridge 10 integrally supports a photosensitive body 11 as an electrostatic latent image bearer, a charging unit 12 that charges the photosensitive body 11, a developing unit 13 that develops an electrostatic latent image formed on the photosensitive body 11 using a developer according to the present invention to form a toner image, and a cleaning unit 14 that cleans toner remaining on the photosensitive body 11 after transferring the toner image formed on the photosensitive body 11 to a recording medium. The process cartridge 10 is attachable to and detachable from a main body of an image forming apparatus (e.g., a copying machine and a printer).

Hereinafter, a method of forming an image using the image forming apparatus in which the process cartridge 10 is installed will be described. First, the photosensitive body 11 is rotationally driven at a predetermined circumferential speed and the circumferential surface of the photosensitive body 11 is uniformly charged to a predetermined positive or negative potential by the charging unit 12. Subsequently, the circumferential surface of the photosensitive body 11 is irradiated with exposure light from an exposure device (not shown), such as a slit exposure-type exposure device or an exposure device that scans and exposes by a laser beam, to form an electrostatic latent image. In addition, the electrostatic latent image formed on the circumferential surface of the photosensitive body 11 is developed by the developing unit 13 using the developer according to the present invention to form a toner image. Subsequently, the toner images formed on the circumferential surface of the photosensitive body 11 are sequentially transferred to a transfer sheet, which is performed in synchronization with the rotation of the photosensitive body 11 and is fed from a paper feeding unit (not shown) to a position between the photosensitive body 11 and a transfer device (not shown). The transfer sheet to which the toner image is transferred is separated from the circumferential surface of the photosensitive body 11 to be introduced to a fixing device (not shown) and the toner image is fixed. After that, the transfer paper is printed out from the image forming apparatus to the outside as a copy (copy). The surface of the photosensitive body 11 after the transfer of the toner image is cleaned by removing the residual toner with the cleaning unit 14. After that, the electrification is removed by a neutralizer (electricity remover) (not shown) and an image is repeatedly formed using the surface of the photosensitive body 11.

Examples

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to the embodiments. Here, "parts" means parts by mass.

(resin Synthesis example 1)

In a flask equipped with a stirrer, 300g of toluene was placed and the temperature was raised to 90 ℃ under a flow of nitrogen. Subsequently, 84.4g (200 mmol:SILAPLANE TM-0701T, manufactured by Chisso Corporation) from CH₂＝CMe-COO-C₃H₆-Si(OSiMe₃)₃A mixture of 3-methacryloxypropyltris (trimethylsiloxy) silane (wherein Me is methyl), 39g (150 mmol) of 3-methacryloxypropylmethyldiethoxysilane, 65.0g (650 mmol) of methyl methacrylate and 0.58g (3 mmol) of 2, 2' -azobis-2-methylbutyronitrile, which is expressed as Me, was added dropwise over 1 hour. After the completion of the dropwise addition, a solution in which 0.06g (0.3 mmol) of 2,2 '-azobis-2-methylbutyronitrile was dissolved in 15g of toluene (total amount of 2, 2' -azobis-2-methylbutyronitrile was 0.64g ═ 3.3 mmol) was further added and the resulting mixture was mixed at 90 ℃ to 100 ℃ for 3 hours and subjected to radical copolymerization to obtain a methacrylic copolymer R1.

(Carrier production example 1)

20 parts of the methacrylic copolymer R1 having a weight average molecular weight of 35,000 obtained in synthesis example 1[ solid content 100% by mass ], 100 parts of a silicone resin solution [ solid content 20% by mass ], 3.0 parts of aminosilane [ solid content 100% by mass ], 36 parts of barium sulfate Fine particles (BARIACE B-55) as Fine particles, which was manufactured by Sakai Chemical Industry co., ltd., long diameter 600nm, and SF-1195), and 60 parts of oxygen-deficient tin (oxyden-deficient tin) Fine particles, which was manufactured by MITSUI & aging co., ltd., primary particle size 30nm, as a catalyst, and 2 parts of diisopropoxy di (titanium ethylacetoacetate) TC-750 (which was manufactured by Matsumoto Fine co., ltd.) were diluted with toluene to obtain a resin solution having a solid content of 20% by mass.

In the case of using Mn ferrite particles having a weight average particle size of 35 μm as core material particles, the resin solution was applied to the core material particles and dried while using an atomizing nozzle in a fluidized bed type coating apparatus and controlling the temperature inside the fluidization to 60 ℃, so that the average film thickness of the resin layer on the surface of the core material particles was 1.00 μm. The obtained carrier was baked in an electric furnace at 210 ℃ for 1 hour to obtain a carrier 1.

(example 2 for production of Carrier)

A carrier 2 corresponding to carrier production example 2 was obtained in exactly the same manner as in carrier production example 1 except for the following: the SF-1 of the fine barium sulfate particles was changed to 250.

(example 3 for production of Carrier)

A carrier 3 corresponding to carrier production example 3 was obtained in exactly the same manner as in carrier production example 1 except for the following: the SF-1 of the fine barium sulfate particles was changed to 210.

(Carrier production example 4)

A carrier 4 corresponding to carrier production example 4 was obtained in exactly the same manner as in carrier production example 1 except for the following: the SF-1 of the fine barium sulfate particles was changed to 170.

(example 5 for production of support)

A carrier 5 corresponding to carrier production example 5 was obtained in exactly the same manner as in carrier production example 1 except for the following: the SF-1 of the fine barium sulfate particles was changed to 160.

(example 6 for production of support)

A carrier 6 corresponding to carrier production example 6 was obtained in exactly the same manner as in carrier production example 1 except for the following: the long diameter of the barium sulfate fine particles was changed to 900 nm.

(example 7 for production of support)

A carrier 7 corresponding to carrier production example 7 was obtained in exactly the same manner as in carrier production example 1 except for the following: the long diameter of the barium sulfate fine particles was changed to 700 nm.

(example 8 for production of support)

A carrier 8 corresponding to carrier production example 8 was obtained in exactly the same manner as in carrier production example 1 except for the following: the long diameter of the barium sulfate fine particles was changed to 500 nm.

(example 9 for production of support)

A carrier 9 corresponding to carrier production example 9 was obtained in exactly the same manner as in carrier production example 1 except for the following: the long diameter of the barium sulfate fine particles was changed to 400 nm.

(Carrier production example 10)

A carrier 10 corresponding to carrier production example 10 was obtained in exactly the same manner as in carrier production example 1 except for the following: the long diameter and SF-1 of the fine barium sulfate particles were changed to 900nm and 250 nm, respectively.

(example 11 for production of support)

A carrier 11 corresponding to carrier production example 11 was obtained in exactly the same manner as in carrier production example 1 except for the following: the long diameter and SF-1 of the fine barium sulfate particles were changed to 400nm and 250, respectively.

(example 12 for production of support)

A carrier 12 corresponding to carrier production example 12 was obtained in exactly the same manner as in carrier production example 1 except for the following: the long diameter and SF-1 of the fine barium sulfate particles were changed to 900nm and 160 nm, respectively.

(example 13 for production of support)

A carrier 13 corresponding to carrier production example 13 was obtained in exactly the same manner as in carrier production example 1 except for the following: the long diameter and SF-1 of the barium sulfate fine particles were changed to 400nm and 160 nm, respectively.

(example 14 for production of support)

The carrier 14 corresponds to the carrier production example 14 and is obtained in exactly the same manner as in the carrier production example 1 except for the following: the fine barium sulfate particles were replaced with magnesium hydroxide (which was manufactured by Sakai Chemical Industry co., ltd., long diameter 600nm, SF-1195).

(example 15 for production of support)

A carrier 15 corresponding to carrier production example 15 was obtained in exactly the same manner as in carrier production example 1 except for the following: the fine barium sulfate particles were replaced with magnesium oxide (which was manufactured by Sakai Chemical Industry co., ltd., long diameter 600nm, SF-1195).

(example 16 for production of support)

A carrier 16 corresponding to carrier production example 16 was obtained in exactly the same manner as in carrier production example 1 except for the following: the fine barium sulfate particles were replaced with hydrotalcite (manufactured by Sakai Chemical Industry co., ltd., long diameter 600nm, SF-1195).

(example 17 for production of support)

A carrier 17 corresponding to carrier production example 17 was obtained in exactly the same manner as in carrier production example 1 except for the following: the fine barium sulfate particles were replaced with zinc oxide (manufactured by Sakai Chemical Industry co., ltd., long diameter 600nm, SF-1195).

(example 18 for production of support)

A carrier 18 corresponding to carrier production example 18 was obtained in exactly the same manner as in carrier production example 1 except for the following: the amounts were changed to 4 parts of methacrylic copolymer R1, 20 parts of silicone resin solution, 0.6 part of aminosilane, 12 parts of fine particles of tin oxide poor and 0.4 part of TC-750. In this example, the thickness of the resin layer on the surface of the core material particle was set to 0.2 μm.

(example 19 for production of support)

A carrier 19 corresponding to carrier production example 19 was obtained in exactly the same manner as in carrier production example 1 except for the following: the amounts were changed to 6 parts of methacrylic copolymer R1, 30 parts of silicone resin solution, 0.9 part of aminosilane, 18 parts of fine particles of tin oxide poor and 0.6 part of TC-750. In this example, the thickness of the resin layer on the surface of the core material particle was set to 0.3 μm.

(example of production of support 20)

The carrier 20 corresponding to the carrier production example 20 was obtained in exactly the same manner as in the carrier production example 1 except for the following: the amounts were changed to 40 parts of methacrylic copolymer R1, 200 parts of silicone resin solution, 6.0 parts of aminosilane, 120 parts of fine particles of tin oxide poor, and 4.0 parts of TC-750. In this example, the thickness of the resin layer on the surface of the core material particle was set to 2.0 μm.

(example 21 for production of support)

A carrier 21 corresponding to carrier production example 21 was obtained in exactly the same manner as in carrier production example 1 except for the following: the amounts were changed to 44 parts of methacrylic copolymer R1, 220 parts of silicone resin solution, 6.6 parts of aminosilane, 132 parts of fine oxygen-deficient tin particles and 4.4 parts of TC-750. In this example, the thickness of the resin layer on the surface of the core material particle was set to 2.2 μm.

(comparative example for production of support 1)

The carrier 22 corresponding to the carrier production comparative example 1 was obtained in exactly the same manner as in the carrier production example 1 except for the following: the SF-1 of the fine barium sulfate particles was changed to 260.

(comparative example for production of support 2)

The carrier 23 corresponding to comparative carrier production example 2 was obtained in exactly the same manner as in carrier production example 1 except for the following: the SF-1 of the fine barium sulfate particles was changed to 150.

(comparative example for production of support 3)

The carrier 24 corresponding to the comparative carrier production example 3 was obtained in exactly the same manner as in the carrier production example 1 except for the following: the long diameter of the fine barium sulfate particles was changed to 1,000 nm.

(comparative example for production of support 4)

The carrier 25 corresponding to comparative carrier production example 4 was obtained in exactly the same manner as in carrier production example 1 except for the following: the long diameter of the barium sulfate fine particles was changed to 300 nm.

(comparative example for production of support 5)

The carrier 26 corresponding to comparative carrier production example 5 was obtained in exactly the same manner as in carrier production example 1 except for the following: the fine barium sulfate particles were replaced with tin oxide-coated barium sulfate (manufactured by Sakai Chemical Industry co., ltd., long diameter 600nm, SF-1195).

< production example of toner >

Synthesis of polyester resin A

A reaction vessel equipped with a condenser, a stirrer and a nitrogen-introducing tube was charged with 65 parts of ethylene oxide 2-mol adduct of bisphenol a, 86 parts of propylene oxide 3-mol adduct of bisphenol a, 274 parts of terephthalic acid and 2 parts of dibutyltin oxide, and the mixture was reacted at 230 ℃ for 15 hours under normal pressure. Subsequently, the mixture was reacted under reduced pressure of 5mmHg to 10mmHg for 6 hours to synthesize a polyester resin. The obtained polyester resin A had a number average molecular weight (Mn) of 2,300, a weight average molecular weight (Mw) of 8,000, a glass transition temperature (Tg) of 58 ℃, an acid value of 25mg KOH/g and a hydroxyl value of 35mg KOH/g.

Synthesis of a prepolymer (a polymer capable of reacting with an active hydrogen group-containing Compound) -

A reaction vessel equipped with a condenser, a stirrer and a nitrogen-introducing tube was charged with 682 parts by mass of an ethylene oxide 2-molar adduct of bisphenol a, 81 parts by mass of a propylene oxide 2-molar adduct of bisphenol a, 283 parts by mass of terephthalic acid, 22 parts by mass of trimellitic anhydride and 2 parts by mass of dibutyltin oxide, and the mixture was reacted at 230 ℃ for 8 hours under normal pressure. Subsequently, the mixture was reacted under reduced pressure of 10mmHg to 15 mmHg for 5 hours to synthesize an intermediate polyester resin.

The obtained intermediate polyester had a number average molecular weight (Mn) of 2,100, a weight average molecular weight (Mw) of 9,600, a glass transition temperature (Tg) of 55 ℃, an acid value of 0.5 and a hydroxyl value of 49.

Subsequently, a reaction vessel equipped with a condenser, a stirrer and a nitrogen-introducing tube was charged with 411 parts by mass of the intermediate polyester, 89 parts by mass of isophorone diisocyanate and 500 parts by mass of ethyl acetate, and the mixture was allowed to react at 100 ℃ for 5 hours to synthesize a prepolymer (a polymer capable of reacting with an active hydrogen group-containing compound).

The obtained prepolymer had a free isocyanate (isocyanate) content of 1.60 mass% and the solid content concentration of the prepolymer (which was after standing at 150 ℃ for 45 minutes) was 50 mass%.

Synthesis of ketimines (active hydrogen group-containing compounds) -

A reaction vessel equipped with a stirring rod and a thermometer was charged with 30 parts by mass of isophorone diamine and 70 parts by mass of methyl ethyl ketone and the mixture was reacted at 50 ℃ for 5 hours to synthesize a ketimine compound (active hydrogen group-containing compound). The obtained ketimine compound (active hydrogen group-containing compound) had an amine value of 423.

Preparation of the masterbatch-

1,000 parts of water, 540 parts of carbon black Printex 35 (manufactured by Degussa AG) having a DBP oil absorption of 42mL/100g and a pH of 9.5, and 1,200 parts of polyester resin a were mixed using a henschel mixer (manufactured by Mitsui Mining co. Subsequently, the obtained mixture was kneaded at 150 ℃ for 30 minutes using a twin-roll machine, and then rolled and cooled. The cooled sheet (sheet) was pulverized by a pulverizer (which is manufactured by Hosokawa Micron Corporation) to prepare a master batch.

Preparation of aqueous media

An aqueous medium was prepared by mixing and stirring 306 parts of ion-exchanged water, 265 parts of a 10 mass% tricalcium phosphate suspension, and 1.0 part of sodium dodecylbenzenesulfonate to uniformly dissolve the mixture.

Measurement of the critical micelle concentration-

The critical micelle concentration of the surfactant (surfactant) was measured by the following method. The analysis was performed using the analysis program in Sigma system using surface tensiometer Sigma (manufactured by KSV Instruments ltd.). The surfactant was added dropwise in an amount of 0.01 wt% with respect to the aqueous medium and the interfacial tension after stirring and allowing to stand was measured. The surfactant concentration at which the interfacial tension is not decreased in the case of dropping the surfactant was determined as the critical micelle concentration using the obtained surface tension curve. The critical micelle concentration of sodium dodecylbenzenesulfonate relative to the aqueous medium was measured by a surface tensiometer Sigma and found to be 0.05 wt% relative to the weight of the aqueous medium.

Preparation of the toner Material liquid

In a beaker, 70 parts of polyester resin a, 10 parts by mass of the prepolymer, and 100 parts of ethyl acetate were charged and dissolved with stirring. To the solution were added 5 parts of paraffin wax (HNP-9, melting point 75 ℃, manufactured by Nippon Seiro co., ltd.), 2 parts of MEK-ST (manufactured by Nissan Chemical Industries, ltd.) and 10 parts of the master batch as a mold release agent. The resulting mixture was treated three times by an Ultra Visco Mill (Ultra-viscous Mill, AIMEX co., Ltd.) as a bead Mill under conditions of a liquid feed rate of 1 kg/hour, a disc peripheral speed of 6 m/sec and a filling rate of 80 volume% of zirconia beads having a particle size of 0.5 mm. After that, 2.7 parts by mass of the ketimine was added and dissolved to prepare a toner material liquid.

Preparation of emulsions or dispersions

A container was charged with 150 parts by mass of the aqueous medium and stirred at a rotation speed of 12,000rpm using a TK-type homomixer (manufactured by Tokushu Kika Kogyo co., ltd.). To this aqueous medium, 100 parts by mass of a toner material dissolved liquid or dispersed liquid was added and the resulting mixture was mixed for 10 minutes to prepare an emulsion or dispersed liquid (emulsified slurry).

Removal of organic solvents

In a flask equipped with a stirrer and a thermometer, 100 parts by mass of the emulsified slurry was charged and desolvated at 30 ℃ for 12 hours while stirring at a stirring peripheral speed of 20 m/min.

-washing-

100 parts by mass of the emulsified slurry was filtered under reduced pressure. Thereafter, 100 parts by mass of ion-exchanged water was added to the filter cake and the resulting mixture was mixed by a TK-type homomixer (at a rotation speed of 12,000rpm for 10 minutes) and then filtered. The following operations were performed twice: 300 parts by mass of ion-exchanged water was added to the obtained filter cake, and the resultant mixture was mixed (at a rotation speed of 12,000rpm for 10 minutes using a TK-type homomixer) and then filtered. To the obtained cake was added 20 parts by mass of a 10 mass% aqueous sodium hydroxide solution and the resulting mixture was mixed using a TK-type homomixer (30 minutes at a rotation speed of 12,000 rpm) and then filtered under reduced pressure. To the obtained filter cake was added 300 parts by mass of ion-exchanged water and the resulting mixture was mixed using a TK-type homomixer (at a rotation speed of 12,000rpm for 10 minutes) and then filtered. The following operations were performed twice: 300 parts by mass of ion-exchanged water was added to the obtained filter cake and the resulting mixture was mixed (at a rotation speed of 12,000rpm for 10 minutes using a TK-type homomixer) and then filtered. To the obtained cake was added 20 parts by mass of 10 mass% hydrochloric acid and the resulting mixture was mixed (at a rotation speed of 12,000rpm for 10 minutes) using a TK-type homomixer and then filtered.

Adjustment of the amount of interfacial activation

To the filter cake obtained by the above washing, 300 parts by mass of ion exchange water was added and the conductivity of the toner dispersion was measured after mixing by a TK-type homomixer (10 minutes at a rotation speed of 12,000 rpm). The surfactant concentration of the toner dispersion was calculated from a calibration curve of the surfactant concentration prepared in advance. Ion-exchanged water was added according to this value to obtain a toner dispersion such that the concentration of the surfactant was a target surfactant concentration of 0.05 wt%.

Surface treatment process

The toner dispersion adjusted to a predetermined surfactant concentration was heated in a water bath at a heating temperature T1 of 55 ℃ for 10 hours while being mixed at 5,000rpm by a TK-type homomixer. Thereafter, the toner dispersion was cooled to 25 ℃ and filtered. To the obtained filter cake was added 300 parts by mass of ion-exchanged water and the resulting mixture was mixed using a TK-type homomixer (at a rotation speed of 12,000rpm for 10 minutes) and then filtered.

Drying-

The obtained final cake was dried at 45 ℃ for 48 hours in a circulating air dryer and sieved using a sieve having a 75 μm mesh size to obtain toner base particles 1.

Treatment with external additives

3.0 parts by mass of hydrophobic silica having an average particle size of 100nm, 1.0 part by mass of titanium oxide having an average particle size of 20nm, and 1.5 parts by mass of hydrophobic silica fine powder having an average particle size of 15nm with respect to 100 parts by mass of the toner base particles 1 were mixed by a henschel mixer to obtain [ toner 1 ].

< preparation of developer >

The [ carriers 1] to [ carrier 26] (930 parts by mass) and the toner 1(70 parts by mass) obtained in examples and comparative examples were mixed and stirred at 81rpm for 5 minutes using a Turbula mixer to prepare [ developers 1] to [ developers 26] for evaluation. A developer for replenishment was prepared using the carrier and the toner so that the toner concentration was 95 mass%.

< evaluation of developer Properties >

In the case of using the obtained developer, images were evaluated using RICOH Pro C7110S (digital color copier/printer multifunction peripheral, manufactured by RICOH co. Specifically, the machine was placed in an environmental evaluation room (an environment of normal temperature and normal humidity of 25 ℃ and 55%) and allowed to stand for one day. Thereafter, in the case of using the developers 1 to 26 and the toner 1 of examples and comparative examples, initial background blurring (fogging), edge carrier adhesion, and solid carrier adhesion were evaluated.

< background blur >

Background blur was evaluated by: the white paper image was stopped during development, the toner on the developed photoreceptor was transferred onto a belt (tape), and its difference (Δ ID) from the image density of the untransferred belt was measured by a 938 spectrodensitometer, which is manufactured by X-Rite inc. The evaluation criteria are as follows:

0 or more and less than 0.005: a (very good)

0.005 or more and less than 0.01: b (good)

0.01 or more and less than 0.02: c (available)

0.02 or more: d (poor)

< edge support adhesion >

An image in which solid portions and blank portions were 170 μm x 170 μm in size as one square formed under development conditions (charging potential (Vd): 630V, developing bias: DC-500V) and alternately arranged in vertical and horizontal directions was output in A3 size and the number of white spots at the square boundaries due to carrier adhesion in the image was counted. The evaluation criteria are as follows:

the amount of carrier adhesion was 0: a (very good)

The number of carrier adhesions is 1 to 3: b (good)

The number of carrier adhesions is 4 to 10: c (available)

The number of carrier adhesions is 11 or more: d (poor)

< adhesion of solid support >

Solid support adhesion was evaluated by: the image formation of the solid image was interrupted and then the number of carrier adhesion on the photoreceptor after transfer was counted using a method of turning off the power during the image formation under predetermined developing conditions (charging potential (Vd): 600V, potential after exposure of a portion corresponding to the image portion (solid image): 100V, and developing bias: DC-500V) and the like. The area to be evaluated was determined as a 10mm x100 mm block on the photoreceptor. The evaluation criteria are as follows:

the amount of carrier adhesion was 0: a (very good)

The number of carrier adhesions is 1 to 3: b (good)

The number of carrier adhesions is 4 to 10: c (available)

The number of carrier adhesions is 11 or more: d (poor)

Subsequently, the running evaluation was performed. In the case of using the developers 1 to 26 and the toner 1 of examples and comparative examples in RICOH Pro C7110S (digital color copier/printer multifunction peripheral, manufactured by RICOH co., ltd.), evaluations of background blur, edge carrier adhesion, and solid carrier adhesion were carried out at an initial stage after running 100,000 copies, 200,000 copies, and 1 million copies at an image area ratio of 40%. The evaluation criteria were the same as above.

The results of the image evaluation are listed in table 1.

TABLE 1

TABLE 1 (continuation)

As is evident from the results of Table 1, the carrier of each example satisfying the conditions that the long diameter of the chargeable fine particles is 400-900nm and the shape factor SF-1 of the chargeable fine particles is 160-250 has sufficient chargeable property, can supply a stable amount of developer to the developing region, and can obtain image quality required in the field of production printing. On the other hand, in each of the comparative examples, all of the above conditions were not satisfied, and thus at least one of the evaluation properties was deteriorated.

Symbol list

1a electrode

1b electrode

2 fluorocarbon resin container

3 vectors

10 Process cartridge

11 photosensitive body

12 charging unit

13 developing part

14 cleaning unit

CITATION LIST

Patent document

PTL 1: japanese patent No.5327500

Claims (8)

1. A carrier for developing an electrostatic latent image, the carrier comprising:

a core material particle and a resin layer covering the surface of the core material particle, wherein

The resin layer comprises a resin and at least two kinds of fine particles;

the at least two types of fine particles include electrically charged fine particles and electrically conductive fine particles;

the charged fine particles have a long diameter of 400-900 nm; and

the charged fine particles have a shape factor SF-1 of 160-250.

2. A carrier for developing an electrostatic latent image according to claim 1, wherein the resin layer has a thickness of 0.2 to 2.0 μm.

3. A two-component developer comprising:

a carrier for electrostatic latent image development according to claim 1 or 2; and

a toner.

4. A two-component developer according to claim 3, wherein the toner is a chromatic toner.

5. A developer for replenishment comprising a carrier and a toner, wherein

The developer includes 2 to 50 parts by mass of the toner with respect to 1 part by mass of the carrier, and

the carrier is the carrier for developing an electrostatic latent image according to claim 1 or 2.

6. An image forming apparatus includes:

an electrostatic latent image bearer;

a charging unit configured to charge the latent image carrier;

an exposure unit configured to form an electrostatic latent image on the latent image carrier;

a developing unit configured to develop the electrostatic latent image formed on the electrostatic latent image carrier using the two-component developer according to claim 3 or 4 to form a toner image;

a transfer unit configured to transfer a toner image formed on the electrostatic latent image carrier to a recording medium; and

a fixing unit configured to fix the toner image transferred to the recording medium.

7. A process cartridge, comprising:

an electrostatic latent image bearer;

a charging unit configured to charge a surface of the electrostatic latent image carrier;

a developing unit configured to develop the electrostatic latent image formed on the electrostatic latent image carrier using the two-component developer according to claim 3 or 4; and

a cleaning unit configured to clean the latent electrostatic image carrier.

8. An image forming method, comprising:

forming an electrostatic latent image on the electrostatic latent image bearer;

developing the electrostatic latent image formed on the electrostatic latent image carrier with the two-component developer according to claim 3 or 4 to form a toner image;

transferring the toner image formed on the electrostatic latent image carrier to a recording medium; and

fixing the toner image transferred to the recording medium.

Images